An oxide transparent conductive film has a low resistance and a high transmittance in the visible region and is utilized for an electrode of a light-receiving device such as a display device such as a liquid crystal display or a solar cell, and particularly, an indium oxide film containing tin is widely utilized as an ITO (indium tin oxide) film.
In recent years, as one means to maximize device properties, improvement of electric properties and optical properties to be fitted for desired characteristics is very important, and with respect to the above ITO film, adjustment of electric properties and optical properties has been attempted by adjusting the amount of tin added, however, it has been difficult to improve both the properties simultaneously. For example, Non-Patent Document 1 discloses a SnO2 amount dependence of electro-optical properties of an In2O3—SnO2 transparent conductive film. According to the document, an In2O3—SnO2 transparent conductive film has a lowest resistance with a SnO2 amount at a level of 10 wt %. However, with such a SnO2 amount, the plasma wavelength shifts to a short wavelength side, and accordingly such a transparent conductive film has a high light absorptivity in the infrared region and has a low transmittance.
Under these circumstances, it has been attempted to improve properties of a sputtering target and a film obtainable by the target, by adding an element to indium oxide.
Patent Document 1 discloses an oxide sintered body comprising indium, at least one element among a plurality of metal elements, and oxygen, wherein the proportion of the selected metal element is from 2.0 to 40 at %. However, Patent Document 1 only discloses an oxide sintered body having the above metal element added singly.
Patent Document 2 discloses an oxide sintered body comprising indium, at least one element among a plurality of metal elements, and oxygen, wherein the proportion of the selected metal element is from 2.2 to 40 at %. Patent Document 2 discloses zirconium, hafnium and tantalum as the metal element, however, it only discloses an example in which zirconium alone is added in an amount of 2.5 at %, an example in which hafnium alone is added in an amount of 2.5 at %, and an example in which tantalum alone is added in an amount of 2.5 at %.
Patent Documents 3 and 4 disclose a sputtering target comprising indium oxide and having an insulating oxide contained, and discloses as the insulating oxide zirconium oxide and hafnium oxide. However, both the documents failed to disclose an example in which zirconium oxide or hafnium oxide is added.